Step 1: Call your cable company provider to find out what kind of cableCards they offer.
Ask, are they Motorola or Scientific Atlantic? If they answer Motorola - ask if they are S-cards or M-cards. You will need 2 S-Cards or 1 M-Card. You may also find out the answer by looking through the Offical Cable Company Sticky. If they SA, you may want to wait.
Step 2: If your cable company offers Motorola cards, then decide how much money you want to spend. The TiVo HD is cheaper and was developed because most folks were too shocked to spend $799 (looks like this has dropped to $599) for the S3. $299 for the TiVo HD impacts the wallet less. What's the difference? - the biggest difference is only recording 20 HD hours vs 32 HD hours. May not seem like much, but it depends on how much TV you plan to record and how fast you will watch. If you don't travel - 20 hours will be enough, but you will feel rushed. What happens is your recordings will disappear before you've had a chance to watch it or it will not record depending on how you have set up your recordings. Most of us TiVoholics do not watch live TV. We record everything and then watch delayed TV. And because you will have dual tuners either way, you will end up recording more. Most of us are multi-TiVo owners, where our S3 is in our main viewing room and have purchased the TiVo HD for our secondary rooms. (I am really waiting for 2 things before I do this - lifetime transfer and multiroom viewing).
Step 3: Hook up your TiVo via your black cable from the wall and run guided set up as the instructions tell you - you want to make sure that hardware is working properly.
Step 4: Be prepared by reading all you can and to follow the directions for the cableCard install provided by TiVo. This is still where the "issues" exist. If you can't follow instructions - do not buy. If your installer is not willing to follow instructions - send him back and ask for a woman (most women read and follow instructions). When the installer agrees to follow your instructions, ask to see the cards. Write the serial numbers of each card on a separate piece of paper. My Motorola Serial Numbers for my S-cards start with NG. Once you put the cards in the slots, you will not be able to see it and you may need to know the number to talk later with the cable company support associate.
Step 4: Know which card is put in Slot 1 by serial number. After you get the 1604 ( :up: correction 161-4 - I was too lazy to look it up and I knew I would be corrected)error and the grey screen comes up, write down the numbers the are on the screen and keep this for each card.
Step 5: Listen to your installer as he/she reads the numbers to the person on the other end of the phone line. Then ask for installer to have the person on the phone read off the same numbers. If there are any differences, it won't work.
Step 6: Repeat Steps 4 and 5
Step 7: Check your channels to make sure you get all of them. Have your channel line up printed off and go to all the channels you currently watch and those new HD ones you may not have watched.
Be prepared for cableCards that don't work. It took me about 4 cards, but as more and more of these cards are tried/fail and are returned - it appears that the cable companies try these deadbeat cards over and over and if it is broken it won't work!
The jury is still out on SA cards. Some have been successful in getting them to work in S3s. TiVo is still working on the TivoHDs. They are planning a fix at the end of the month (when they say this it could be the end of any month - you can never be sure when fixing stuff like this how long it will take).
Overall - I have been very happy with my S3, but I have spent $1000 for my S3 and another $250 for the eSata drive. I have gone through pixelation issues that have come, gone, come and right now gone. I do think it is worth it.